In packaging of pastes, creams, and topical ointments, a collapsible tube is often used. The packaging permits storage of the product in the absence of air and other possible contaminants. Tubes are made from drawn metal or laminated foils and films depending on the characteristics desired of the tube and the sensitivity of the contents to contamination by external elements.
One drawback of collapsible tubes and the products contained therein is the inability to quickly and accurately measure quantities dispensed from such tubes. Usually, such tubes hold viscous pastes, creams, gels and the like which do not flow easily. Therefore, such substances are difficult to dispense in accurate amounts.
The viscous nature of the substances can cause a user to believe that he or she has a certain quantity of dispensed when the actual amount is far greater or far less. This has leant itself to often describing the amount of product dispensed in terms of the length of a strip of product extruded by squeezing the collapsible tube. However, this method is subject to each individual's perception of length and the substantial errors associated therewith.
U.S. Pat. No. 2,904,227 discloses a metering device for a squeeze-type container. The device uses a piston and metering chamber structure. The piston uncovers the metering chamber when the piston is in a first position. Movement of the piston to an extended position closes off the metering chamber and dispenses fluid through a conduit having end ports. The disclosure explains that the device is limited to low viscosity substances. The device relies on the internal container pressure to move the piston. In use, it is difficult to tell whether the piston has fully extended or to provide sufficient pressure to dispense high viscosity products such as creams and pastes.
U.S. Pat. No. 3,338,475 discloses a device for dispensing liquids or creams. The device operates in the form of a single shot pump. That is, the device has a resilient pump unit with a check valve at each end. The unit is squeezed to force the product out through the check valve at the outlet end. The resiliency of the unit then expands the chamber closing the outlet check valve and pulling product into the chamber through a check valve at the container neck. The resiliency of the unit must be sufficient to pull viscous substances from the container. Thus, the more viscous the substance, the more force that is necessary to overcome the resiliency of the unit. Furthermore, there is no positive indication of when a "dose" has been administered. Rather, the dose size is a function of the size and strength of the user's fingers as well as the depth of the compression of the unit.
U.S. Pat. No. 4,376,495 describes a device for dispensing an adjustable dose from a flexible container. The device has a hollow piston structure which moves within a neck of a container. The piston moves to a position against stops at the end of the neck to prevent further flow of container contents. To reset the dose, a central pin is inserted to push the piston back. A valve in the piston is concurrently opened to permit flow of a portion of the contents from one side of the piston to the other thus allowing piston movement. The initial position that the piston is returned to determines the quantity of contents dispensed at the next usage.
Other U.S. patents disclosing valve or dosing assemblies for dispensing containers are U.S. Pat. Nos. 4,564,131 and 4,607,762.
The above-described devices lack an ease of operation and a reliability necessary for many consumer products. A consumer must be able to easily and quickly determine that an appropriate amount of a substance has been dispensed, but the described devices lack the requisite ease of operation.
SUMMARY OF THE INVENTION
The invention relates to a dosing and dispensing apparatus which supplies a measured dose of a viscous product from a container. The apparatus is sealingly attached to the container by, for example, a threaded or snap connection.
A conduit of the apparatus extends from the container and communicates with the contents of the container. When product is expelled or drawn out of the container, it is directed through the conduit.
At an end of the conduit is an expandable dosing chamber. The dosing chamber receives product which flows from the container through the conduit. The dosing chamber has a predetermined minimum and maximum volume. Advantageously, the dosing chamber may be formed by a slidable cap which is telescopingly received on the conduit. The cap slides between expanded and contracted positions which respectively define the maximum and minimum dosing chamber volumes.
A check valve is associated with the conduit and prevents flow of product through the conduit into the container when the dosing chamber is collapsed.
A discharge opening is defined by the dosing chamber through which product contained in the dosing chamber is discharged when the chamber is collapsed. The flow through this opening is controlled, however, by a back pressure means. The back pressure means prevents flow through the discharge opening when the pressure within the chamber is at or below the pressure necessary to expand the chamber and permits flow at pressures greater than that necessary to expand the chamber. Thus, product being transferred into the chamber will not exit the chamber until the chamber is fully expanded. Any attempt increase in internal pressure merely expands the chamber which in turn prevents the pressure from expelling the product.